We didn’t always have the option to eat all day long. Our hunter-gatherer ancestors would go days, even weeks, with no food yet managed to cope and survive under these conditions. Before the advent of agriculture 10,000 years ago food availability was highly unpredictable, in abundance in the summer and scarce in winter. Fasting has been a natural part of our evolution and practiced for millennia by all faiths as a means of “cleansing” the body and mind, yet today medical authorities warn us of the dangers of missing a meal (or even a snack).

Hippocrates, the godfather of modern medicine, over 2,000 years ago stated the treatment for weight gain “should include exertion and eating only once a day” while the ancient Greek writer Plutarch remarked “instead of using medicine, better fast today.” Fast-forward to the middle ages and renowned Swiss German doctor and scientist Paracelsus wrote “fasting is the greatest remedy – the physician within”, while Benjamin Franklin also believed “the best of all medicines is fasting.”

Let’s take a closer look at the physiology of fasting, then explore some of its potential benefits.

What Happens During Fasting?

Fasting is the controlled and voluntary removal of all food for a specific period of time. When you fast, your body’s blood sugar and insulin levels begin to fall. To ensure your body (and brain) have energy, your liver releases its glycogen carbohydrate stores to supply organs with glucose and keep blood sugars stable. You typically have enough glycogen in your liver, and muscles, to keep you going for 24-36 hours. Once you’ve exhausted your glycogen stores, your liver produces glucose from the amino acids (via a process called gluconeogenesis).

After two to three days, your low insulin levels will stimulate the breakdown of triglycerides, the kind of fat found in your body-fat stores. The triglyceride is broken down in its three free fatty acids that can be used by virtually all tissues for energy (except your brain) and glycerol backbone is used to make more glucose.

To keep your brain happy, your liver begins to produce ketones – beta-hydroxybutyrate and acetoacetate – which provide your brain with approximately 75% of its fuel requirements. Ketone production can ramp up as much as 70x during fasting. Lastly, during fasting your body pumps out significant amounts of growth hormone (GH) in order to preserve muscle mass and lean tissue.

The Benefits of Fasting

In the early 20th century, the Journal of Biological Chemistry described fasting as a “perfectly safe, harmless and effective method for reducing the weight of those suffering from obesity.” Let’s review some of the benefits of fasting for weight loss and blood sugar and insulin control.

1) Simplicity

Fasting is very straight-forward; do not eat. You can drink coffee, tea or bone broth but do not eat. Dietary advice that is simple is the most effective, and it doesn’t get simpler than “do not eat”.

2) Cost-Effective

Fasting is free. No expensive medications, supplements or superfoods.

3) Convenient

Fasting can be done anywhere, no equipment, supplements or special foods required.

4) Flexible

It doesn’t matter if you’re vegan, Paleo or anything in between... . Fasting fits any dietary approach or individual.

5) Lowers Insulin

Chronically high insulin levels are associated with weight gain, and high triglycerides levels, dramatically increasing your risk of heart disease. Low-carb and keto diets are both terrific for reducing insulin levels, however fasting is truly the biggest “metabolic hammer” for lowering chronically high insulin levels and reversing insulin resistance. (If you’re on diabetes medications, talk to your doctor before starting any new fasting protocol.)

High levels of small, dense LDL cholesterol, as well as high triglycerides mentioned above and lipoprotein (a) all serve as reliable markers for cardiovascular disease risk. Fasting has been shown to reduce all three of these parameters. It makes sense that if you abstain from food, your body will breakdown its own fat stores to fuel activity, thus improving your lipid profile.

If you’re overweight, pre-diabetic or diabetic (type-2) fasting can be a powerful tool to reversing chronically high blood sugar and insulin levels, poor metabolic health and CVD risk. Today’s constant snacking society and plethora of processed foods has no doubt contributed to the current obesity and diabetes epidemic. Fasting is a simple, effective and cost-efficient strategy to improve your health.

Dr. Marc Bubbs ND, CISSN, CSCS

Ps. To learn more check out my recent interview with obesity and diabetes expert Dr. Jason Fung MD who uses fasting regularly in his practice.

Dr. Marc Bubbs

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Dr. Marc Bubbs ND, MS(c), CISSN, CSCS is a Naturopathic Doctor, Speaker, Director of Nutrition for the Canadian Men's National Basketball Team and former Strength Coach. Dr. Bubbs is the author of The Paleo Project: The 21st Century Guide to Looking Leaner, Getting Stronger, and Living Longerand a regular contributor to Re-Find Health, Breaking Muscle,PaleoDiet.com anda nutrition advisory board member forStrong Magazine. Dr. Bubbs regularly presents at health, fitness and medical conferences across Canada, USA, UK and Europe and has consulted with professional sports teams in the NBA, NFL, NHL and MLB.